Re: [PATCH] Revert "serial: 8250_dw: Fix runtime PM handling"

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Oct 01, 2018 at 09:42:37PM -0700, Guenter Roeck wrote:
> This reverts commit d76c74387e1c978b6c5524a146ab0f3f72206f98.
> 
> While commit d76c74387e1c ("serial: 8250_dw: Fix runtime PM handling")
> fixes runtime PM handling when using kgdb, it introduces a traceback for
> everyone else.

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

However, I would prefer to have a better solution as Tony already spelled out.

> 
> BUG: sleeping function called from invalid context at
> 	/mnt/host/source/src/third_party/kernel/next/drivers/base/power/runtime.c:1034
> in_atomic(): 1, irqs_disabled(): 1, pid: 1, name: swapper/0
> 7 locks held by swapper/0/1:
>  #0: 000000005ec5bc72 (&dev->mutex){....}, at: __driver_attach+0xb5/0x12b
>  #1: 000000005d5fa9e5 (&dev->mutex){....}, at: __device_attach+0x3e/0x15b
>  #2: 0000000047e93286 (serial_mutex){+.+.}, at: serial8250_register_8250_port+0x51/0x8bb
>  #3: 000000003b328f07 (port_mutex){+.+.}, at: uart_add_one_port+0xab/0x8b0
>  #4: 00000000fa313d4d (&port->mutex){+.+.}, at: uart_add_one_port+0xcc/0x8b0
>  #5: 00000000090983ca (console_lock){+.+.}, at: vprintk_emit+0xdb/0x217
>  #6: 00000000c743e583 (console_owner){-...}, at: console_unlock+0x211/0x60f
> irq event stamp: 735222
> __down_trylock_console_sem+0x4a/0x84
> console_unlock+0x338/0x60f
> __do_softirq+0x4a4/0x50d
> irq_exit+0x64/0xe2
> CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.19.0-rc5 #6
> Hardware name: Google Caroline/Caroline, BIOS Google_Caroline.7820.286.0 03/15/2017
> Call Trace:
>  dump_stack+0x7d/0xbd
>  ___might_sleep+0x238/0x259
>  __pm_runtime_resume+0x4e/0xa4
>  ? serial8250_rpm_get+0x2e/0x44
>  serial8250_console_write+0x44/0x301
>  ? lock_acquire+0x1b8/0x1fa
>  console_unlock+0x577/0x60f
>  vprintk_emit+0x1f0/0x217
>  printk+0x52/0x6e
>  register_console+0x43b/0x524
>  uart_add_one_port+0x672/0x8b0
>  ? set_io_from_upio+0x150/0x162
>  serial8250_register_8250_port+0x825/0x8bb
>  dw8250_probe+0x80c/0x8b0
>  ? dw8250_serial_inq+0x8e/0x8e
>  ? dw8250_check_lcr+0x108/0x108
>  ? dw8250_runtime_resume+0x5b/0x5b
>  ? dw8250_serial_outq+0xa1/0xa1
>  ? dw8250_remove+0x115/0x115
>  platform_drv_probe+0x76/0xc5
>  really_probe+0x1f1/0x3ee
>  ? driver_allows_async_probing+0x5d/0x5d
>  driver_probe_device+0xd6/0x112
>  ? driver_allows_async_probing+0x5d/0x5d
>  bus_for_each_drv+0xbe/0xe5
>  __device_attach+0xdd/0x15b
>  bus_probe_device+0x5a/0x10b
>  device_add+0x501/0x894
>  ? _raw_write_unlock+0x27/0x3a
>  platform_device_add+0x224/0x2b7
>  mfd_add_device+0x718/0x75b
>  ? __kmalloc+0x144/0x16a
>  ? mfd_add_devices+0x38/0xdb
>  mfd_add_devices+0x9b/0xdb
>  intel_lpss_probe+0x7d4/0x8ee
>  intel_lpss_pci_probe+0xac/0xd4
>  pci_device_probe+0x101/0x18e
> ...
> 
> Revert the offending patch until a more comprehensive solution
> is available.
> 
> Cc: Tony Lindgren <tony@atomide.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Phil Edworthy <phil.edworthy@renesas.com>
> Fixes: d76c74387e1c ("serial: 8250_dw: Fix runtime PM handling")
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/tty/serial/8250/8250_dw.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> index fa8dcb470640..d31b975dd3fd 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -630,10 +630,6 @@ static int dw8250_probe(struct platform_device *pdev)
>  	if (!data->skip_autocfg)
>  		dw8250_setup_port(p);
>  
> -#ifdef CONFIG_PM
> -	uart.capabilities |= UART_CAP_RPM;
> -#endif
> -
>  	/* If we have a valid fifosize, try hooking up DMA */
>  	if (p->fifosize) {
>  		data->dma.rxconf.src_maxburst = p->fifosize / 4;
> -- 
> 2.7.4
> 

-- 
With Best Regards,
Andy Shevchenko